Cosign supports the v0.2 SLSA predicate through the --type slsaprovenance flag on the attest and attest-blob commands. SLSA 1.0 Release Candidate 1 (RC1) is out and RC2 should be coming out today. By the end of this month (April 2023) it is expected that SLSA v1.0 will be officially released. We don't expect any new major changes to the SLSA provenance predicate.

For reference, here's the specification for the predicate: https://slsa.dev/provenance/v1-rc1